The Descent of Man

ments than the males, and could not escape so
well from danger. Hence, with animals in a
state of nature, we must rely on mere estimation,
in order to judge of the proportions of the
sexes at maturity; and this is but little trustworthy,
except when the inequality is strongly
marked. Nevertheless, as far as a judgment can
be formed, we may conclude from the facts
given in the supplement, that the males of some
few mammals, of many birds, of some fish and
insects, are considerably more numerous than
the females.
The proportion between the sexes fluctuates
slightly during successive years: thus with racehorses,
for every 100 mares born the stallions
varied from 107.1 in one year to 92.6 in another
year, and with greyhounds from 116.3 to 95.3.
But had larger numbers been tabulated throughout
an area more extensive than England, these
fluctuations would probably have disappeared;
and such as they are, would hardly suffice